\begin{table}%t1
%\centering
\par
\caption{\label{abu} Chemical compositions
of the white dwarf envelope models in mass fractions. 
$Z_{\rm s}$ contains metals (all elements except H and He) in solar
fraction. $\delta$$X_{i}$ indicates the extra mass
fraction of element \emph{i} beyond that included in $Z_{\rm s}$. The total
abundance of metals is indicated by $Z_{\rm total}$.}
\par
\begin{tabular}{ c c c c c c c c c }
\hline\hline
\noalign{\smallskip}
WD & Mixing & Name & $X$ & $Y$ & $Z_{\rm s}$ & & & $Z _{\rm total}$ \\
\hline 
\noalign{\smallskip}
 & & & & & & $\delta X_{\rm O}$ & $\delta X_{\rm Ne}$  & \\
\hline 
\noalign{\smallskip}
ONe & 75\% & ONe75 & 0.18 & 0.08 & 0.12 & 0.38 & 0.24 & 0.74 \\
ONe & 50\% & ONe50 & 0.35 & 0.15 & 0.09 & 0.25 & 0.16 & 0.5 \\
ONe & 25\% & ONe25 & 0.53 & 0.2 & 0.06 & 0.13 & 0.08 & 0.27 \\
\hline 
\noalign{\smallskip}
 & & & & & & $\delta  X_{\rm C}$ & $\delta  X_{\rm O}$ & \\
\hline
\noalign{\smallskip}
CO & 50\% & CO50 & 0.35 & 0.14 & 0.02 & 0.245 & 0.245 & 0.51 \\
\hline 
\end{tabular}
\end{table}